all entities must be added to the entity manifest and the count at the top adjusted.

Entity.manifest is in the main folder, where it should be copied over to your mod's main folder, outside the various data folders.

That entry is in English.str.  Open it up, do a search for that entry, and the line below it should contain the description for the Sova.

That's either going to be easy, or much trickier.  If you want to tie it to an existing research, the just add the research in as a prerequisite to your entity.

[code]

Prerequisites
    NumResearchPrerequisites 1
    ResearchPrerequisite
        Subject "<Research>"
        Level 1
    RequiredFactionNameID ""
    RequiredCompletedResearchSubjects 0

[/code]

Should look like that when you're finished.

If you want to make a new research, then you're going to have to copy one of the existing ship unlock ones with a new name, add it to the PlayerRace.entity file, then add that in as the needed research.  You don't need to add .entity to the end in there, only the name.